PSI - Issue 17

Jessica Taylor et al. / Procedia Structural Integrity 17 (2019) 472–478 Jessica Taylor/ Structural Integrity Procedia 00 (2019) 000 – 000

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This work has shown that: • The parameters which influence the crack arrest behavior of modern structural steels are independent of those which provide these steels with upper-shelf fracture toughness. • The crack arrest behavior is more closely linked to the ductile to brittle transition temperature of the steel (as characterized by T 27J from Charpy tests) – even for steels where the NDTT would lie on the upper shelf of the Charpy transition curve. • High CTOD fracture toughness is not sufficient to determine whether the steel could be at risk of unstable fracture from a localized brittle event, due to poor crack arrest toughness. This test program will be continued in future work. Quantitative crack arrest testing will be carried out on a selection of the steels to compare to and validate the small scale predictions. Electron Back Scatter Diffraction (EBSD) will be used to characterize fully the texture of the materials by including the grain orientation and correlating the materials’ texture to its small-scale mechanical properties. Further correlations between mechanical and microstructural properties will be investigated for each of the materials to determine the relationship between microstructure and arrest. If there remains to be no correlation, it is advised that an energy based approach is investigated to predict the arrest behavior of the materials i.e. K ca . The five materials studied here will be compared with available material data in the literature to expand the correlations which have been made. The experimental program will be continued on more steels to strengthen the argument for new small-scale test methods for predicting crack arrestibility. Acknowledgements This publication was made possible by the sponsorship and support of Lloyds Register Foundation with the mentorship of Weihong He from Lloyds Register. Lloyd’s Register Foundation helps to protect life and property by supporting engineering-related education, public engagement and the application of research. The work was enabled through, and undertaken at, the National Structural Integrity Research Centre (NSIRC), a postgraduate engineering facility for industry-led research into structural integrity established and managed by TWI through a network of both national and international Universities. This work was supported by grant EP/L016303/1 for Cranfield University, Strathclyde University and the University of Oxford, Centre for Doctoral Training in Renewable Energy Marine Structures - REMS (http://www.rems-cdt.ac.uk/) from the UK Engineering and Physical Sciences Research Council (EPSRC). Special thanks go to the Armourers and Brasiers’ Company, whose financial support through their postgraduate travel grant scheme was essential to attend this conference. I am very grateful for this opportunity and for being chosen for this prestigious award. The efforts of Tom Woolhouse were appreciated in getting the specimens machined by The Test House. The testing work was performed by the technicians in the fracture lab at TWI including Jerry Godden, Jack Bradford and Phil Cossey, whose involvement in this work is greatly appreciated. The metallurgical expertise of Ashley Spencer and Joanna Nicholas was vital when it came to analyzing the microstructure of these steels, particularly with sample 7. Future work

preparation. References

ASTM (2000) ‘E208 Standar d Test Method for Conducting Drop-Weight Test to Determine Nil-Ductility Transition Temperature of Ferritic Steels 1’, Test, 06(Reapproved), pp. 1– 13. doi: 10.1520/E0208-06R12.2. ASTM (2007) ‘E1221 Standard Test Method for Determining Plane -Strain Crack-Arrest Fracture Toughness, KIa, of Ferritic Steels’, 96(Reapproved), pp. 1– 19. doi: 10.1520/E1221-12A.2. ASTM (2014) ' ASTM E436-03 (2014) Standard Test Method for Drop-Weight Tear Tests of Ferritic Steels.' ASTM International, 2014. doi: https://doi.org/10.1520/E0436-03R14 '